Difference between revisions of "CSC231 Powers of 2 in Python"

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(→‎A Python Program that overflows (or not))
(→‎Exercise: A Python Program that loops forever...)
 
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[[CSC231_Class_Page | Back to Weekly Schedule]]
 
[[CSC231_Class_Page | Back to Weekly Schedule]]
 
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=A Python Program that overflows (or not)=
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--[[User:Thiebaut|D. Thiebaut]] 13:57, 8 October 2010 (UTC)
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<code><pre>
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This Exercise is a companion to the [[CSC231 C++ Program and infinite loops |same exercise implemented in C++]].
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<br />
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=Exercise: Powers of 2 in Python...=
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<br />
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* First do the exercise with C++ mentioned above.
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* Then create the program below, and run it.  It will wait you to press Enter at every loop, so that you can control the speed of the loop.
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* What happens when you reach 2147483648, and press Enter a few times?  How is that different from the C++ approach?  Why?
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<br />
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==The Program==
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<br />
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<source lang="python">
 
# mulby2.py
 
# mulby2.py
 
# D. Thiebaut
 
# D. Thiebaut
 
# csc231
 
# csc231
 
# demonstrates how python changes type of
 
# demonstrates how python changes type of
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# variable as computation progresses.  Check
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# variable as computation progresses.  Compare
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# how an interpreted language would react in this
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# this to how a compiled language would react in this
 
# situation (mulby2.cpp)
 
# situation (mulby2.cpp)
  
 
x = 0x1
 
x = 0x1
 
print "starting value of x = ", x
 
print "starting value of x = ", x
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curType = type( x )
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print "type( x ) = ", type( x )
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#curType = type( x )
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#print "type( x ) = ", type( x )
  
 
while ( True ):
 
while ( True ):
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     x = x * 2
 
     x = x * 2
 
     print "x = ", x
 
     print "x = ", x
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    raw_input(  "> " )
 
     continue
 
     continue
  
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         break
 
         break
  
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</pre></code>
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</source>
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[[Category:CSC231]][[Category:Python]]

Latest revision as of 12:18, 13 November 2014

Back to Weekly Schedule

--D. Thiebaut 13:57, 8 October 2010 (UTC)

This Exercise is a companion to the same exercise implemented in C++.



Exercise: Powers of 2 in Python...


  • First do the exercise with C++ mentioned above.
  • Then create the program below, and run it. It will wait you to press Enter at every loop, so that you can control the speed of the loop.
  • What happens when you reach 2147483648, and press Enter a few times? How is that different from the C++ approach? Why?


The Program


# mulby2.py
# D. Thiebaut
# csc231
# demonstrates how python changes type of
# variable as computation progresses.  Compare 
# this to how a compiled language would react in this
# situation (mulby2.cpp)

x = 0x1
print "starting value of x = ", x

#curType = type( x )
#print "type( x ) = ", type( x )

while ( True ):
    lastx = x
    x = x * 2
    print "x = ", x
    raw_input(  "> " )
    continue

    if type( x )!= type( lastx ):
        print "last x = ", lastx
        print "type( last x ) = ", type( lastx ) 
        print "x = ", x
        print "type( x ) = ", type(x)
        break









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